Making glexecwn more user-friendly

Dear developers,

I've compiled a list of changes to your package which will make it hopefully easier to use (also #1).
The changes are already in production at our cluster (SL6, Puppet 3.3.0).

They include:
- simplifications of the structure, using parameters instead of inherit from params [e9a0e4e, 0f1f318] 
- fixed to dependencies and module name (Modulefile, metadata.json) [46d1391]
- fixes to puppet style guide [f49e559]
- fixing loose parameters and unnecessary includes [6582d62, a5a0644]
- replacing unknown classes [0998097]

Some of the above changes are necessary to make this module work outside cernops.

Generally, whenever a new parameter is introduced I've added it into params so it matches the default which was originally set.

Please test it in your environment just to make sure that you experience no changes to your system.